The present invention relates generally to compounds and methods for enhancing immune responses in patients, as well as in isolated cells and cell cultures. The invention is more particularly related to compounds comprising all or a portion of a Leishmania antigen that is a homologue of the eukaryotic initiation factor 4A (eIF4A), and to the use of such compounds in vaccines for stimulating immune responses.
Vaccines commonly induce immunity to an infection or a disease by generating an immune response in a patient to a specific antigen associated with the infection or disease. Modern techniques for the identification and use of appropriate antigens have the potential to lead to the testing and development of a large number of vaccines specific for common infections (including bacterial, viral and protozoan infections), as well as diseases such as cancer.
However, in many cases, purified antigens are weak immunogens, i.e., the immune response generated by a specific antigen, while directed against the desired target, is not of a sufficient magnitude to confer immunity. In such cases, an immunomodulating agent, such as an adjuvant or immunostimulant, must be employed to enhance the immune response. Adjuvants are substances that enhance a specific immune response to an antigen when injected with the antigen or at the same site as the antigen. Such substances function by a variety of mechanisms, including (1) trapping the antigen, and releasing it slowly, (2) stimulating migration of cells to the injection site, (3) stimulating or trapping lymphocytes, or stimulating lymphocyte proliferation and (4) improving antigen dispersion within the patient""s body. For example, oils, polymers, mineral salts and liposomes have been used as adjuvants in this regard. By comparison, immunostimulants are substances that induce a general, temporary increase in a patient""s immune response, whether administered with the antigen or separately. Typical immunostimulants are bacterial, such as BCG (an attenuated strain of Mycobacterium tuberculosis) or a nonviable form of Corynebacterium parvum. By either mechanism, the adjuvant or immunostimulant serves to enhance the desired specific immune response by non-specific means.
A serious drawback of many of the adjuvants currently available is their toxicity. In general, the best adjuvants (i.e., those that provide the greatest enhancement of the desired immune response) are also the most toxic. Thus, practitioners must continually balance the level of stimulation against the toxicity of the adjuvant.
Accordingly, there is a need in the art for the identification of compounds that provide a desired enhancement of specific immune responses, but with low levels of toxicity. The present invention fulfills these needs and further provides other related advantages.
Briefly stated, the present invention provides compounds and methods relating to the Leishmania antigen LbeIF4A or LmeIF4A, which is homologous to the eukaryotic ribosomal protein eIF4A. In one aspect of the invention, methods are provided for enhancing or eliciting an immune response to an antigen and/or an antigen encoded by a DNA vaccine in a patient, comprising administering to a patient an antigen and/or a DNA vaccine, and an LbeIF4A polypeptide comprising an amino acid sequence encoded by a DNA sequence selected from the group consisting of: (a) nucleotides 115-1323 of SEQ ID NO. 1; and (b) DNA sequences that hybridize to a nucleotide sequence complementary to nucleotides 115-1323 of SEQ ID NO. 1 under moderately stringent conditions, wherein the DNA sequence encodes a polypeptide that stimulates a Th1 immune response in a peripheral blood mononuclear cells obtained from a Leishmania-infected individual. In another aspect of the invention, methods are provided for enhancing or eliciting an immune response to an antigen and/or an antigen encoded by a DNA vaccine, in a patient, comprising administering to a patient an antigen and/or a DNA vaccine, and an LmeIF4A polypeptide comprising an amino acid sequence encoded by a DNA sequence selected from the group consisting of: (a) nucleotides 117 through 1325 of SEQ ID NO:3; and (b) DNA sequences that hybridize to a nucleotide sequence complementary to nucleotides 117 through 1325 of SEQ ID NO:3 under moderately stringent conditions, wherein the DNA sequence encodes a polypeptide that stimulates a Th1 immune response in peripheral blood mononuclear cells obtained from a Leishmania-infected individual.
In related aspects, the present invention provides methods for enhancing an immune response to an antigen and/or an antigen encoded by a DNA vaccine in a patient, comprising administering to a patient an antigen and/or a DNA vaccine, and an LbeIF4A polypeptide comprising amino acids 49-403 of SEQ ID NO: 2, or a variant thereof that differs only in conservative substitutions and/or modifications, or an antigen and/or a DNA vaccine and an LmeIF4A polypeptide comprising amino acids 49-403 of SEQ ID NO: 4, or a variant thereof that differs only in conservative substitutions and/or modifications.
In another related aspect, methods are provided for enhancing an immune response in a biological sample, comprising contacting a biological sample with an antigen and/or an antigen encoded by a DNA vaccine, and an LbeIF4A polypeptide as described above, wherein the biological sample comprises cells selected from the group consisting of peripheral blood mononuclear cells, monocytes, B cells, dendritic cells, and combinations thereof.
In yet another related aspect, methods are provided for enhancing or eliciting an immune response in a biological sample, comprising contacting a biological sample with an LmeIF4A polypeptide as described above, wherein the biological sample comprises cells selected from the group consisting of peripheral blood mononuclear cells, monocytes, B cells, dendritic cells and combinations thereof.
In another aspect, methods are provided for enhancing an immune response to a tumor in a patient, comprising administering to a patient a tumor antigen or antigens and/or a DNA vaccine, and an LbeIF4A or an LmeIF4A polypeptide as described above.
Within further aspects, methods are provided for treating a tumor in a patient, comprising administering to a patient an LbeIF4A or LmeIF4A polypeptide, as described above.
Within each of the aspects noted above, as an alternative to utilizing an LbeIF4A or LmeIF4A polypeptide, one can utilize viral vectors or nucleic acid molecules (collectively, the xe2x80x9cnucleic acid compositionsxe2x80x9d) directing the expression of the polypeptide in patient cells infected or transfected with the nucleic acid compositions. The step of administering the nucleic acid composition may be performed in vivo or ex vivo, the latter including the subsequent administration of the infected/transfected cells. In addition, where an antigen or tumor antigen is administered, it will be evident that the nucleic acid composition may also be designed to direct the expression of such antigens (either on the same or different vectors or molecules).
Within further aspects, methods are provided for treating a Th2-mediated disease in a patient, comprising administering to a patient (a) an LeIF4A polypeptide; (b) a nucleic acid molecule directing the expression of an LeIF4A polypeptide in patient cells transfected with the nucleic acid molecule or (c) a viral vector directing the expression of an LeIF4A polypeptide in patient cells infected with the viral vector. Th2-mediated diseases include asthma, allergy, Th2 mediated autoimmune disease and Helminth infection.
The present invention further provides methods for decreasing production of one or more Th2-associated cytokines in a patient, comprising administering to a patient (a) an LeIF4A polypeptide; (b) a nucleic acid molecule directing the expression of an LeIF4A polypeptide in patient cells transfected with the nucleic acid molecule or (c) a viral vector directing the expression of an LeIF4A polypeptide in patient cells infected with the viral vector. Within certain embodiments, the Th2-associated cytokine is IL-4 or IL-5.
Methods for stimulating or enhancing IL-18 production in a patient are also provided, comprising administering to a patient (a) an LeIF4A polypeptide; (b) a nucleic acid molecule directing the expression of an LeIF4A polypeptide in patient cells transfected with the nucleic acid molecule or (c) a viral vector directing the expression of an LeIF4A polypeptide in patient cells infected with the viral vector.
Within further aspects, methods are provided for enhancing or eliciting an immune response to an antigen in a biological sample, comprising contacting a biological sample with an LeIF4A polypeptide in combination with one or more Th1-associated cytokines.
The present invention also provides method for enhancing or eliciting an immune response to an antigen in a patient, comprising administering to a patient one or more Th1-associated cytokines in combination with (a) an LeIF4A polypeptide; (b) a nucleic acid molecule directing the expression of an LeIF4A polypeptide in patient cells transfected with the nucleic acid molecule or (c) a viral vector directing the expression of an LeIF4A polypeptide in patient cells infected with the viral vector. The Th1-associated cytokines may be IL-2, IL-12, IL-15 and/or IL-18.